In current fixed, mobile, and internet protocol (IP) telephony networks, a call that is initiated by a telephony terminal, e.g., a fixed phone, mobile phone, IP phone, or software, is setup according to a route determined by a switch that is deployed centrally in the network. The route used for the call is based on the called destination number and may involve multiple interconnected networks. Typically, a route is chosen according to a number of policies set by the network operators, such as to optimize utilization of available resources or minimize costs for the call.
As an example, FIG. 1 illustrates an existing telephony network 100. A mobile terminal 101 is connected to the core network 103 through a radio access network 102. The user of the mobile terminal 101, or an application executed on mobile terminal 101, can establish a communication session with a destination that is reachable through the core network 103. A communication session may, e.g., be a call to another mobile terminal 105, connected to the core network 103 via a radio access network 104, or to a fixed phone 106. If the core network 103 is connected via 107 to an IP network 108, such as the internet, the call can also be routed to a voice-over-IP (VoIP) capable terminal 109. In general, a communication session is not limited to voice services but may also be established for the purpose of communicating data, e.g., surfing on the world wide web (WWW) by accessing a web server 110, or connecting to a corporate network 111.
Today's mobile phones are typically capable of establishing wireless network connections by virtue of several wireless network technologies, e.g., GSM (Global System for Mobile communications), UMTS (Universal Mobile Telecommunications System), and WLAN (wireless local area network). As an example, with reference to FIG. 1, the mobile terminal 101 can connect to a GSM/UMTS radio access network 102 via a voice connection 112 and/or a data connection 113. Further, the mobile terminal 101 can also establish a connection 114 with a WLAN 115 through a WLAN access point.
Despite the increasing number of possible call routes from a telephony terminal to a destination, the choice of the actual call route is rather rigid and typically limited to a few options, depending on whether the user initiates a voice call or an application running on the telephony terminal requests a data connection.
For example, if the user of a mobile terminal 101 initiates a call, the core network 103 will typically decide how to route the call to its destination. If, on the other hand, the mobile terminal 101 is capable of setting up VoIP calls, e.g., through an application such as Skype, the mobile terminal 101 will route the call over an IP connection to its destination, either over a GSM/UMTS data connection 113 or over a WLAN connection 114. Further, the user can setup a call using services like call-back or two-stage dialing, which are provided by a service provider 119.
As the number of choices to setup a call from a telephony terminal increases, it becomes more complex for users to keep track of different access networks and costs.